Polarizing plate, polarizing plate manufacturing method, and optical apparatus

ABSTRACT

To provide a polarizing plate capable of excellently controlling reflectance characteristics, a polarizing plate manufacturing method, and an optical apparatus including the polarizing plate. Provided is a polarizing plate 10 with a wire grid structure, including: a transparent substrate 1 and a grid-shaped convex portion 6 arranged on the transparent substrate at a pitch shorter than a wavelength of light of a use band and extending in a predetermined direction, wherein the grid-shaped convex portion 6 includes a reflection layer 2, a first dielectric layer 3, and an absorption layer 4 in order from the transparent substrate 1, and wherein the reflection layer and the first dielectric layer have substantially the same width and a minimum width of the absorption layer is smaller than a minimum width of the reflection layer and the first dielectric layer as viewed from a predetermined direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority fromJapanese Patent Application No. 2017-253277, filed on 28 Dec. 2017, andU.S. patent application Ser. No. 16/230,619, filed on Dec. 21, 2018,titled “POLARIZING PLATE, POLARIZING PLATE MANUFACTURING METHOD, ANDOPTICAL APPARATUS HAVING SPECIFIED MINIMUM WIDTH OF ABSORPTION LAYER”.The content of both of these applications is incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a polarizing plate, a polarizing platemanufacturing method, and an optical apparatus.

Related Art

Conventionally, as a polarizing element, there has been proposed anabsorption wire grid type polarizing element which cancels lightreflected from a metal grating by an interference effect and transmitsthe other polarized light component by forming a metal grating on asubstrate at a pitch shorter than a wavelength of light of a use bandand forming a dielectric layer and an inorganic particle layer on themetal grating. In such a polarizing element, in recent years, there hasbeen a request for controlling reflectance characteristics under theenvironment of strong light together with high transmittancecharacteristics as the brightness of a liquid crystal projectorincreases.

Here, the reflectance characteristics are determined by the interferencebetween layers constituting a lattice structure or the absorption intothe layer. Then, a method of controlling the reflectance by using amaterial satisfying a request for a dielectric layer or the like isproposed (see Patent Document 1). However, in Patent Document 1, sincethe layers are designed in a rectangular shape, it is difficult to forma perfect rectangular shape in a nano level and thus it is verydifficult to design a material with a shape.

Further, there is proposed a method of controlling reflectancecharacteristics of a polarizing element obtained by forming a finepattern on a resinous base material before forming a metal layer andcontrolling a reflectance and a wavelength of the base material (seePatent Document 2). However, since the base material used in PatentDocument 2 is formed of resin, heat resistance or light resistance ispoor as compared with a wire grid polarizing element formed of aninorganic material. As a result, there is concern for a long-term useunder the environment of strong light.

Patent Document 1: Japanese Unexamined Patent Application (Translationof PCT Application), Publication No. 2010-530994 Patent Document 2:Japanese Unexamined Patent Application, Publication No. 2015-212741

SUMMARY OF THE INVENTION

The invention has been made in view of the above-described circumstancesand an object of the invention is to provide a polarizing plate capableof excellently controlling reflectance characteristics, a polarizingplate manufacturing method, and an optical apparatus including thepolarizing plate.

The inventor has found a polarizing plate which can excellently controlreflectance characteristics by using an effect of shifting a wavelengthrange of a light absorbing action in a polarizing plate having a wiregrid structure including a transparent substrate and a grid-shapedconvex portion arranged on the transparent substrate at a pitch shorterthan a wavelength of light of a use band and extending in apredetermined direction, in which the grid-shaped convex portionincludes a reflection layer, a first dielectric layer, and an absorptionlayer in order from the transparent substrate and a relationship ofminimum widths of the reflection layer, the first dielectric layer, andthe absorption layer as viewed from the predetermined direction isspecified. As a result, the inventor has contrived the invention.

That is, an aspect of the invention is to provide a polarizing plate(for example, a polarizing plate 10 to be described later) with a wiregrid structure, including: a transparent substrate (for example, atransparent substrate 1 to be described later) and a grid-shaped convexportion (for example, a grid-shaped convex portion 6 to be describedlater) arranged on the transparent substrate at a pitch shorter than awavelength of light of a use band and extending in a predetermineddirection, in which the grid-shaped convex portion includes a reflectionlayer (for example, a reflection layer 2 to be described later), a firstdielectric layer (for example, a first dielectric layer 3 to bedescribed later), and an absorption layer (for example, an absorptionlayer 4 to be described later) in order from the transparent substrate,and in which as viewed from the predetermined direction, the reflectionlayer and the first dielectric layer are formed to have substantiallythe same width and the minimum width of the absorption layer is smallerthan the minimum width of the reflection layer and the first dielectriclayer.

A second dielectric layer may be provided on a surface opposite to thefirst dielectric layer in the absorption layer and the minimum width ofthe absorption layer may be smaller than a minimum width of the seconddielectric layer as viewed from the predetermined direction.

The reflection layer may be substantially rectangular as viewed from thepredetermined direction.

The first dielectric layer may be substantially rectangular as viewedfrom the predetermined direction.

The transparent substrate may be transparent to a wavelength of light ofa use band and may be formed of glass, crystal, or sapphire.

The reflection layer may be formed of aluminum or aluminum alloy.

The first dielectric layer may be formed of Si oxide.

The second dielectric layer may be formed of Si oxide.

The absorption layer may include Fe or Ta and also include Si.

A surface of the polarizing plate to which light is incident may becovered with a protection film formed of a dielectric.

The surface of the polarizing plate to which light is incident may becovered with an organic water-repellent film.

Further, another aspect of the invention is to provide a method ofmanufacturing a polarizing plate with a wire grid structure, including:a reflection layer forming step of forming a reflection layer on onesurface of a transparent substrate; a first dielectric layer formingstep of forming a first dielectric layer on a surface opposite to thetransparent substrate in the reflection layer; an absorption layerforming step of forming an absorption layer on a surface opposite to thereflection layer in the first dielectric layer; and an etching step offorming a grid-shaped convex portion to be arranged on the transparentsubstrate at a pitch shorter than a wavelength of light of a use band byselectively etching a formed lamination structure, in which in theetching step, the reflection layer and the first dielectric layer areformed to have substantially the same width and a minimum width of theabsorption layer is set to be smaller than a minimum width of reflectionlayer and the first dielectric layer by combining isotropic etching andanisotropic etching.

Further, another aspect of the invention is to provide an opticalapparatus including the polarizing plate.

According to the invention, it is possible to provide the polarizingplate capable of excellently controlling reflectance characteristics,the polarizing plate manufacturing method, and the optical apparatusincluding the polarizing plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic diagram illustrating a polarizingplate according to an embodiment of the invention.

FIG. 2 is a cross-sectional schematic diagram illustrating a polarizingplate according to an embodiment with a conventional structure.

FIG. 3 is a graph showing a result obtained by verifying a relationshipbetween a wavelength and an absorption axis reflectance for a polarizingplate illustrated in FIG. 1 and a polarizing plate illustrated in FIG. 2optimized to a green band (wavelength λ=520 to 590 nm) by simulation.

FIG. 4 is a graph showing a result obtained by verifying a relationshipbetween the wavelength and the absorption axis reflectance for thepolarizing plate illustrated in FIG. 1 and the polarizing plateillustrated in FIG. 2 optimized to a blue band (wavelength λ=430 to 510nm) by simulation.

FIG. 5 is a graph showing a result obtained by verifying a relationshipbetween the wavelength and the absorption axis reflectance for thepolarizing plate illustrated in FIG. 1 and the polarizing plateillustrated in FIG. 2 optimized to a red band (wavelength λ=600 to 680nm) by simulation.

FIG. 6 is a graph showing a result obtained by verifying a relationshipbetween a volume of an absorption layer and an absorption axisreflectance in a green band (wavelength λ=520 to 590 nm) for thepolarizing plate illustrated in FIG. 1 and the polarizing plateillustrated in FIG. 2 optimized to the green band (wavelength λ=520 to590 nm) by simulation.

FIG. 7 is a graph showing a result obtained by verifying a relationshipbetween the volume of the absorption layer and the absorption axisreflectance in a blue band (wavelength λ=430 to 510 nm) for thepolarizing plate illustrated in FIG. 1 and the polarizing plateillustrated in FIG. 2 optimized to the blue band (wavelength λ=430 to510 nm) by simulation.

FIG. 8 is a graph showing a result obtained by verifying a relationshipbetween the volume of the absorption layer and the absorption axisreflectance in a red band (wavelength λ=600 to 680 nm) for thepolarizing plate illustrated in FIG. 1 and the polarizing plateillustrated in FIG. 2 optimized to the red band (wavelength λ=600 to 680nm) by simulation.

FIG. 9 is a cross-sectional schematic diagram illustrating a polarizingplate according to an embodiment of the invention.

FIG. 10 is a cross-sectional schematic diagram illustrating a polarizingplate according to an embodiment with a conventional structure.

FIG. 11 is a graph showing a result obtained by verifying a relationshipbetween a wavelength and an absorption axis reflectance for a polarizingplate illustrated in FIG. 9 and a polarizing plate illustrated in FIG.10 optimized to a green band (wavelength λ=520 to 590 nm) by simulation.

FIG. 12 is a graph showing a result obtained by verifying a relationshipbetween the wavelength and the absorption axis reflectance for thepolarizing plate illustrated in FIG. 9 and the polarizing plateillustrated in FIG. 10 optimized to a blue band (wavelength λ=430 to 510nm) by simulation.

FIG. 13 is a graph showing a result obtained by verifying a relationshipbetween the wavelength and the absorption axis reflectance for thepolarizing plate illustrated in FIG. 9 and the polarizing plateillustrated in FIG. 10 optimized to a red band (wavelength λ=600 to 680nm) by simulation.

FIG. 14 is a graph showing a result obtained by verifying a relationshipbetween the volume of the absorption layer and the absorption axisreflectance in a green band (wavelength λ=520 to 590 nm) for thepolarizing plate illustrated in FIG. 9 and the polarizing plateillustrated in FIG. 10 optimized to the green band (wavelength λ=520 to590 nm) by simulation.

FIG. 15 is a graph showing a result obtained by verifying a relationshipbetween the volume of the absorption layer and the absorption axisreflectance in a blue band (wavelength λ=430 to 510 nm) for thepolarizing plate illustrated in FIG. 9 and the polarizing plateillustrated in FIG. 10 optimized to the blue band (wavelength λ=430 to510 nm) by simulation.

FIG. 16 is a graph showing a result obtained by verifying a relationshipbetween the volume of the absorption layer and the absorption axisreflectance in a red band (wavelength λ=600 to 680 nm) for thepolarizing plate illustrated in FIG. 9 and the polarizing plateillustrated in FIG. 10 optimized to the red band (wavelength λ=600 to680 nm) by simulation.

FIG. 17 is a cross-sectional schematic diagram illustrating a polarizingplate according to an embodiment of the invention.

FIG. 18 is a cross-sectional schematic diagram illustrating a polarizingplate according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the invention will be described in detailwith reference to the drawings.

Polarizing Plate

A polarizing plate of the invention is a polarizing plate having a wiregrid structure including a transparent substrate and a grid-shapedconvex portion arranged on the transparent substrate at a pitch shorterthan a wavelength of light of a use band and extending in apredetermined direction. Further, the grid-shaped convex portionincludes at least a reflection layer, a first dielectric layer, and anabsorption layer in order from the transparent substrate. Additionally,the polarizing plate of the invention may include layers other than thetransparent substrate, the reflection layer, the first dielectric layer,and the absorption layer as long as the effect of the invention isexhibited.

FIG. 1 is a cross-sectional schematic diagram illustrating a polarizingplate 10 according to an embodiment of the invention. As illustrated inFIG. 1, the polarizing plate 10 includes a transparent substrate 1 whichis transparent to light of a use band and a grid-shaped convex portion 6which is arranged on one surface of the transparent substrate 1 at apitch shorter than a wavelength of light of a use band. The grid-shapedconvex portion 6 includes a reflection layer 2, a first dielectric layer3, and an absorption layer 4 in order from the transparent substrate 1.That is, the polarizing plate 10 has a wire grid structure in which thegrid-shaped convex portion 6 formed by laminating the reflection layer2, the first dielectric layer 3, and the absorption layer 4 in orderfrom the transparent substrate 1 is arranged on the transparentsubstrate 1 in a one-dimensional lattice shape.

Here, as illustrated in FIG. 1, the extension direction of thegrid-shaped convex portion 6 (the predetermined direction) will bereferred to as a Y-axis direction. Further, a direction which isorthogonal to the Y-axis direction and in which the grid-shaped convexportion 6 is arranged on the main surface of the transparent substrate 1will be referred to as an X-axis direction. In this case, the lightwhich is incident to the polarizing plate 10 is incident from adirection orthogonal to the X-axis direction and the Y-axis direction ata position in which the grid-shaped convex portion 6 is formed on thetransparent substrate 1.

The polarizing plate with the wire grid structure attenuates thepolarized wave (TE wave (S wave)) having an electric field componentparallel to the Y-axis direction and transmits the polarized wave (TMwave (P wave)) having an electric field component parallel to the X-axisdirection by using four functions of transmission, reflection,interference, and selective light absorption of polarized waves byoptical anisotropy. Thus, in FIG. 1, the Y-axis direction indicates thedirection of the absorption axis of the polarizing plate and the X-axisdirection indicates the direction of the transmission axis of thepolarizing plate.

The light which is incident from a position provided with thegrid-shaped convex portion 6 in the polarizing plate 10 illustrated inFIG. 1 is attenuated while being partially absorbed when passing throughthe absorption layer 4 and the first dielectric layer 3. In the lighttransmitted through the absorption layer 4 and the first dielectriclayer 3, the polarized wave (TM wave (P wave)) is transmitted throughthe reflection layer 2 with high transmittance. Meanwhile, in the lighttransmitted through the absorption layer 4 and the first dielectriclayer 3, the polarized wave (TE wave (S wave)) is reflected by thereflection layer 2. The TE wave which is reflected by the reflectionlayer 2 is partially absorbed and reflected when passing through theabsorption layer 4 and the first dielectric layer 3 and then the lightis returned to the reflection layer 2. Further, the TE wave which isreflected by the reflection layer 2 is attenuated by interference whenpassing through the absorption layer 4 and the first dielectric layer 3.When the TE wave is selectively attenuated as described above, thepolarizing plate 10 can obtain desired polarizing characteristics.

As illustrated in FIG. 1, the grid-shaped convex portion of thepolarizing plate of the invention includes the reflection layer 2, thefirst dielectric layer 3, and the absorption layer 4 as viewed from theextension direction of each one-dimensional lattice (a predetermineddirection), that is, in a cross-sectional view orthogonal to thepredetermined direction.

Here, a dimension of the specification will be described with referenceto FIG. 1. The height means a dimension in a direction perpendicular tothe main surface of the transparent substrate 1 in FIG. 1. The width Wmeans a dimension in the X-axis direction orthogonal to the heightdirection as viewed from the Y-axis direction along the extensiondirection of the grid-shaped convex portion 6. Further, an interval inthe X-axis direction of the grid-shaped convex portion 6 when thepolarizing plate 10 is viewed from the Y-axis direction along theextension direction of the grid-shaped convex portion 6 will be referredto as a pitch P.

In the polarizing plate of the invention, the pitch P of the grid-shapedconvex portion is not particularly limited as long as the pitch isshorter than the wavelength of light of a use band. From the viewpointof ease of production and stability, the pitch P of the grid-shapedconvex portion is preferably, for example, 100 nm to 200 nm. The pitch Pof the grid-shaped convex portion can be measured by the observationusing a scanning electron microscope or a transmission electronmicroscope. For example, when the pitch P at four arbitrary positions ismeasured by using the scanning electron microscope or the transmissionelectron microscope, the arithmetic mean value thereof can be set to thepitch P of the grid-shaped convex portion. Hereinafter, this measurementmethod will be referred to as electron microscopy.

In the polarizing plate of the invention, as viewed from the extensiondirection of the grid-shaped convex portion (a predetermined direction:the Y-axis direction), the reflection layer and the first dielectriclayer are formed to have substantially the same width and the minimumwidth of the absorption layer is smaller than the minimum width of thereflection layer and the first dielectric layer. Accordingly, it ispossible to realize the polarizing plate capable of excellentlycontrolling the reflectance characteristics.

Transparent Substrate

The transparent substrate (the transparent substrate 1 in FIG. 1) is notparticularly limited as long as the substrate has translucency for thelight of a use band and can be appropriately selected in accordance witha purpose. The “translucency for the light of a use band” does not meanthat the transmittance of the light of a use band is 100% and may be thetranslucency capable of keeping the function as the polarizing plate. Asthe light of a use band, for example, visible light having a wavelengthof about 380 nm to 810 nm can be exemplified.

The shape of the main surface of the transparent substrate is notparticularly limited and a shape (for example, a rectangular shape) isappropriately selected according to a purpose. An average thickness ofthe transparent substrate is preferably, for example, 0.3 mm to 1 mm.

As a material forming the transparent substrate, a material having arefractive index of 1.1 to 2.2 is preferable and glass, crystal,sapphire, or the like can be exemplified. From the viewpoint of cost andtransmittance, glass, particularly, quartz glass (a refractive index of1.46) or soda lime glass (a refractive index of 1.51) is preferablyused. The composition of the components of the glass material is notparticularly limited and, for example, an inexpensive glass materialsuch as silicate glass widely distributed as optical glass can be used.

Further, from the viewpoint of thermal conductivity, crystal or sapphirehaving high thermal conductivity is preferably used. Accordingly, sincehigh light resistance against strong light is obtained, the polarizingplate is preferably used as a polarizing plate for an optical engine ofa projector with a large heat generation amount.

Further, when a transparent substrate formed of optically activecrystals such as crystal is used, it is preferable to dispose thegrid-shaped convex portion 6 in a direction parallel to or perpendicularto the optical axis of the crystal. Accordingly, excellent opticalcharacteristics can be obtained. Here, the optical axis indicates adirection axis in which a difference in refractive index between 0(ordinary ray) and E (extraordinary ray) of the light traveling in thatdirection becomes minimal.

Reflection Layer

The reflection layer (the reflection layer 2 in FIG. 1) is formed on onesurface of the transparent substrate and a metal film extending in aband shape is arranged in the Y-axis direction which is the absorptionaxis. Additionally, in the invention, different layers may exist betweenthe transparent substrate and the reflection layer.

The reflection layer 2 of the polarizing plate 10 according to anembodiment of the invention illustrated in FIG. 1 extends in a directionperpendicular to the plane direction of the transparent substrate 1 andhas a rectangular shape as viewed from the extension direction of thegrid-shaped convex portion (a predetermined direction: the Y-axisdirection), that is, in a cross-sectional view orthogonal to thepredetermined direction. The reflection layer has a function of a wiregrid type polarizer and is used to attenuate the polarized wave (TE wave(S wave)) having an electric field component parallel to thelongitudinal direction of the reflection layer and to transmit thepolarized wave (TM wave (P wave)) having an electric field componentorthogonal to the longitudinal direction of the reflection layer.

A material of forming the reflection layer is not particularly limitedas long as the material has reflectance for the light of a use band. Forexample, a single element such as Al, Ag, Cu, Mo, Cr, Ti, Ni, W, Fe, Si,Ge, and Te or an alloy including one or more of these elements can beexemplified. Among these, the reflection layer is preferably formed ofaluminum or aluminum alloy. Additionally, in addition to these metalmaterials, for example, an inorganic film or a resin film other than ametal formed with a high surface reflectance may be formed by coloringor the like.

The film thickness of the reflection layer is not particularly limitedand is preferably, for example, 100 nm to 300 nm. Additionally, the filmthickness of the reflection layer can be measured by, for example, theabove-described electron microscopy.

In the polarizing plate of the invention, the width of the reflectionlayer needs to be substantially the same as that of the first dielectriclayer to be described later and the minimum width thereof needs to belarger than the minimum width of the absorption layer to be describedlater. According to the invention, it is possible to realize thepolarizing plate capable of excellently controlling the reflectancecharacteristics. Although the width of the reflection layer depends onthe relationship with the pitch P of the grid-shaped convex portion, thewidth is preferably, for example, 35 nm to 45 nm. Additionally, thewidth can be measured by, for example, the above-described electronmicroscopy.

As a method of setting the minimum width of the reflection layer to belarger than the minimum width of the absorption layer, for example, amethod of changing a balance using a combination of isotropic etchingand anisotropic etching can be exemplified.

First Dielectric Layer

The first dielectric layer (the first dielectric layer 3 in FIG. 1) isformed on the reflection layer and the dielectric film extending in aband shape is arranged in the Y-axis direction corresponding to theabsorption axis. Additionally, in the invention, different layers mayexist between the reflection layer and the first dielectric layer.

The first dielectric layer 3 of the polarizing plate 10 according to anembodiment of the invention illustrated in FIG. 1 is laminated on thereflection layer to be perpendicular to the plane direction of thetransparent substrate 1 and has a rectangular shape as viewed from theextension direction of the grid-shaped convex portion (a predetermineddirection: the Y-axis direction), that is, in a cross-sectional vieworthogonal to the predetermined direction.

The film thickness of the first dielectric layer is formed in a range inwhich polarized light reflected by the absorption layer is transmittedthrough the absorption layer and the phase of the polarized lightreflected by the reflection layer is shifted by a half wavelength.Specifically, the film thickness of the first dielectric layer isappropriately set to a range of 1 to 500 nm capable of improving aninterference effect by adjusting the phase of the polarized light. Thefilm thickness of the first dielectric layer can be measured by, forexample, the above-described electron microscopy.

As a material forming the first dielectric layer, general materials likeSi oxide such as SiO₂, metal oxide such as Al₂O₃, beryllium oxide, andbismuth oxide, MgF₂, cryolite, germanium, titanium dioxide, silicon,magnesium fluoride, boron nitride, boron oxide, boron oxide, tantalumoxide, carbon, or a combination thereof can be exemplified. Among these,the first dielectric layer 3 is preferably formed of Si oxide.

The refractive index of the first dielectric layer is preferably largerthan 1.0 and equal to or smaller than 2.5. Since the opticalcharacteristics of the reflection layer are also influenced by theperipheral refractive index, it is possible to control polarizingcharacteristics by selecting the material of the first dielectric layer.

Further, when the film thickness or the refractive index of the firstdielectric layer is appropriately adjusted, the TE wave reflected by thereflection layer can be returned to the reflection layer while beingpartially reflected when the light is transmitted through the absorptionlayer. Accordingly, it is possible to attenuate the light passingthrough the absorption layer by interference. In this way, when the TEwave is selectively attenuated, desired polarizing characteristics canbe obtained.

In the polarizing plate of the invention, the width of the firstdielectric layer needs to be substantially the same as that of thereflection layer and the minimum width thereof needs to be larger thanthe minimum width of the absorption layer to be described below.According to the invention, it is possible to realize the polarizingplate capable of excellently controlling the reflectancecharacteristics. Although the width of the first dielectric layerdepends on the relationship with the pitch P of the grid-shaped convexportion, the width is preferably, for example, 35 nm to 45 nm.Additionally, the width can be measured by, for example, theabove-described electron microscopy.

Absorption Layer

The absorption layer (the absorption layer 4 in FIG. 1) is formed on thefirst dielectric layer and is arranged to extend in a band shape in theY-axis direction corresponding to the absorption axis. In the invention,as viewed from the Y-axis direction (a predetermined direction)corresponding to the absorption axis, the minimum width of theabsorption layer is set to be smaller than the minimum width of thereflection layer and the first dielectric layer. In the invention, sincethe absorption layer has the above-described shape, it is possible toexhibit an effect of shifting the wavelength range of the lightabsorbing action. As a result, it is possible to realize the polarizingplate capable of excellently controlling the reflectancecharacteristics.

The absorption layer 4 of the polarizing plate 10 according to anembodiment of the invention illustrated in FIG. 1 has a substantiallyisosceles trapezoidal shape as viewed from the extension direction ofthe grid-shaped convex portion (a predetermined direction: the Y-axisdirection), that is, in a cross-sectional view orthogonal to thepredetermined direction and has a taper shape in which a side surface isinclined in a direction in which a width is narrowed toward the frontend side (the opposite side of the transparent substrate 1).

In the embodiment, the maximum width of the absorption layer 4 becomesthe width of the outermost surface near the transparent substrate 1 inthe absorption layer 4 and is substantially the same as the maximumwidth of the reflection layer 2 and the first dielectric layer 3 havinga rectangular shape as viewed from the extension direction of thegrid-shaped convex portion 6 (a predetermined direction: the Y-axisdirection), that is, in a cross-sectional view orthogonal to thepredetermined direction.

Further, the minimum width of the absorption layer 4 becomes the widthof the outermost surface opposite to the transparent substrate 1 in theabsorption layer 4 and is smaller than the minimum width of thereflection layer 2 and the first dielectric layer 3 having a rectangularshape as viewed from the extension direction of the grid-shaped convexportion 6 (a predetermined direction: the Y-axis direction), that is, ina cross-sectional view orthogonal to the predetermined direction.

As the material forming the absorption layer, one or more materialswhich have a light absorbing action and in which an extinction constantof an optical constant is not zero like a metal material, asemiconductor material or the like can be exemplified and thesematerials are appropriately selected depending on the wavelength rangeof light to be applied. As the metal material, a single element such asTa, Al, Ag, Cu, Au, Mo, Cr, Ti, W, Ni, Fe, and Sn or an alloy includingat least one of these elements can be exemplified. Further, as thesemiconductor material, Si, Ge, Te, ZnO, and silicide materials(β-FeSi₂, MgSi₂, NiSi₂, BaSi₂, CrSi₂, CoSi₂, TaSi, and the like) can beexemplified. By using these materials, the polarizing plate 10 canobtain a high extinction ratio with respect to the visible light rangeto be applied. Among these, it is preferable that the absorption layerinclude Fe or Ta and further include Si.

When the semiconductor material is used as the absorption layer, theband gap energy of the semiconductor is involved in the absorptionaction and hence the band gap energy needs to be equal to or smallerthan the use band. For example, when the material is used in visiblelight, it is necessary to use a material having absorption at awavelength of 400 nm or more, that is, a material having a band gap of3.1 eV or less.

The film thickness of the absorption layer is not particularly limitedand is preferable, for example, 10 nm to 100 nm. The film thickness ofthe absorption layer 4 can be measured by, for example, theabove-described electron microscopy.

Additionally, the absorption layer can be formed as a high-density filmby a sputtering method or a vapor deposition method. Further, theabsorption layer may be formed as two or more layers by differentmaterials.

Although the maximum width of the absorption layer depends on therelationship with the pitch P of the grid-shaped convex portion, themaximum width is preferably, for example, 35 nm to 45 nm. Further, themaximum width of the absorption layer may be substantially the same asthe width of, for example, the first dielectric layer located below theabsorption layer. Additionally, the width can be measured by, forexample, the above-described electron microscopy.

As described above, in the invention, as viewed from the Y-axisdirection (a predetermined direction) corresponding to the absorptionaxis, the minimum width of the absorption layer needs to be smaller thanthe minimum width of the reflection layer and the first dielectriclayer. According to the invention, it is possible to realize thepolarizing plate capable of excellently controlling the reflectancecharacteristics. A ratio of the minimum width of the absorption layerwith respect to the maximum width of the absorption layer is preferably,for example, smaller than 100% and in the range of 60 to 90%.Additionally, the width can be measured by, for example, theabove-described electron microscopy.

Diffusion Barrier Layer

The polarizing plate of the invention may include the diffusion barrierlayer between the first dielectric layer and the absorption layer. Thatis, in the polarizing plate illustrated in FIG. 1, the grid-shapedconvex portion 6 includes the reflection layer 2, the first dielectriclayer 3, the diffusion barrier layer, and the absorption layer 4 inorder from the transparent substrate 1. Since the diffusion barrierlayer is provided, the diffusion of the light on the absorption layer isprevented. This diffusion barrier layer can be formed by a metal film ofTa, W, Nb, or Ti.

Protection Film

Further, the light incident surface of the polarizing plate of theinvention may be covered with a protection film formed by a dielectricin a range in which a change in optical characteristic is notinfluenced. The protection film is formed by a dielectric film and canbe formed on, for example, the surface of the polarizing plate (thesurface provided with the wire grid) by using a chemical vapordeposition (CVD) or an atomic layer deposition (ALD). Accordingly, it ispossible to suppress an oxidation reaction more than necessary for themetal film.

Organic Water-repellent Film

Further, the light incident surface of the polarizing plate of theinvention may be covered with an organic water-repellent film. Theorganic water-repellent film is formed of a fluorine-based silanecompound such as perfluorodecyltriethoxysilane (FDTS) and can be formedby using, for example, the above-described CVD or ALD. Accordingly, itis possible to improve reliability such as moisture resistance of thepolarizing plate.

Further, the invention is not limited to the above-described embodimentillustrated in FIG. 1 and modification and improvement within the scopeof achieving the object of the invention are included in the invention.

FIG. 9 is a cross-sectional schematic diagram illustrating a polarizingplate 30 according to another embodiment of the invention. Thepolarizing plate 30 illustrated in FIG. 9 has the same configuration asthat of the polarizing plate 10 illustrated in FIG. 1 except that thesecond dielectric layer 5 is formed on the absorption layer 4 of thepolarizing plate 10 illustrated in FIG. 1 in the grid-shaped convexportion 6.

Second Dielectric Layer

The second dielectric layer 5 of the polarizing plate 30 illustrated inFIG. 9 is laminated on the absorption layer to be perpendicular to theplane direction of the transparent substrate 1 and has a rectangularshape as viewed from the extension direction of the grid-shaped convexportion (a predetermined direction: the Y-axis direction), that is, in across-sectional view orthogonal to the predetermined direction. Further,in the polarizing plate 30 illustrated in FIG. 9, the width of thesecond dielectric layer 5 is the same as the width of the firstdielectric layer 3.

The film thickness, the material, the refractive index, the shape, andthe like of the second dielectric layer are the same as those of thefirst dielectric layer.

In the embodiment illustrated in FIG. 9, the maximum width of theabsorption layer 4 becomes the width of the outermost surface near thetransparent substrate 1 in the absorption layer 4 and is substantiallythe same as the maximum width of the reflection layer 2 and the firstdielectric layer 3 having a rectangular shape as viewed from theextension direction of the grid-shaped convex portion 6 (a predetermineddirection: the Y-axis direction), that is, in a cross-sectional vieworthogonal to the predetermined direction.

Further, the minimum width of the absorption layer 4 becomes the widthof the outermost surface opposite to the transparent substrate 1 in theabsorption layer 4 and is smaller than the minimum width of thereflection layer 2 and the first dielectric layer 3 having a rectangularshape as viewed from the extension direction of the grid-shaped convexportion 6 (a predetermined direction: the Y-axis direction), that is, ina cross-sectional view orthogonal to the predetermined direction.

FIG. 17 is a cross-sectional schematic diagram illustrating a polarizingplate 50 according to another embodiment of the invention. Thepolarizing plate 50 illustrated in FIG. 17 has a configuration in whichthe second dielectric layer 5 is formed on the absorption layer 4 in thegrid-shaped convex portion 6 and has the same configuration as that ofthe polarizing plate 30 illustrated in FIG. 9 except that the shape ofthe absorption layer 4 is different.

The absorption layer 4 of the polarizing plate 50 illustrated in FIG. 17has a substantially isosceles trapezoidal shape as viewed from theextension direction of the grid-shaped convex portion (a predetermineddirection: the Y-axis direction), that is, in a cross-sectional vieworthogonal to the predetermined direction and has a taper shape in whicha side surface is inclined in a direction in which a width is narrowedtoward the front end side (the opposite side of the transparentsubstrate 1).

In the embodiment illustrated in FIG. 17, the maximum width of theabsorption layer 4 becomes the width of the outermost surface oppositeto the transparent substrate 1 in the absorption layer 4 and issubstantially the same as the maximum width of the reflection layer 2and the first dielectric layer 3 having a rectangular shape as viewedfrom the extension direction of the grid-shaped convex portion 6 (apredetermined direction: the Y-axis direction), that is, in across-sectional view orthogonal to the predetermined direction.

Further, the minimum width of the absorption layer 4 becomes the widthof the outermost surface near the transparent substrate 1 in theabsorption layer 4 and is smaller than the minimum width of thereflection layer 2 and the first dielectric layer 3 having a rectangularshape as viewed from the extension direction of the grid-shaped convexportion 6 (a predetermined direction: the Y-axis direction), that is, ina cross-sectional view orthogonal to the predetermined direction.

FIG. 18 is a cross-sectional schematic diagram illustrating a polarizingplate 60 according to another embodiment of the invention. Thepolarizing plate 60 illustrated in FIG. 18 has a configuration in whichthe second dielectric layer 5 is formed on the absorption layer 4 in thegrid-shaped convex portion 6 and has the same configuration as that ofthe polarizing plate 30 illustrated in FIG. 9 except that the shape ofthe absorption layer 4 is different.

The absorption layer 4 of the polarizing plate 60 illustrated in FIG. 18has a shape in which the substantially center in the film thicknessdirection has the minimum width and a side portion contacting the firstdielectric layer and the second dielectric layer has a maximum width asviewed from the extension direction of the grid-shaped convex portion (apredetermined direction: the Y-axis direction), that is, in across-sectional view orthogonal to the predetermined direction.

In the embodiment illustrated in FIG. 18, the maximum width of theabsorption layer 4 becomes the length of the side portion contacting thefirst dielectric layer and the second dielectric layer and issubstantially the same as the maximum width of the reflection layer 2and the first dielectric layer 3 having a rectangular shape as viewedfrom the extension direction of the grid-shaped convex portion 6 (apredetermined direction: the Y-axis direction), that is, in across-sectional view orthogonal to the predetermined direction.

Further, the minimum width of the absorption layer 4 becomes the widthof the substantially center portion of the absorption layer 4 in thefilm thickness direction and is smaller than the minimum width of thereflection layer 2 and the first dielectric layer 3 having a rectangularshape as viewed from the extension direction of the grid-shaped convexportion 6 (a predetermined direction: the Y-axis direction), that is, ina cross-sectional view orthogonal to the predetermined direction.

Polarizing Plate Manufacturing Method

A polarizing plate manufacturing method of the invention includes areflection layer forming step, a first dielectric layer forming step, anabsorption layer forming step, and an etching step.

In the reflection layer forming step, the reflection layer is formed onone surface of the transparent substrate. In the first dielectric layerforming step, the first dielectric layer is formed on the reflectionlayer formed by the reflection layer forming step. In the absorptionlayer forming step, the absorption layer is formed on the firstdielectric layer formed by the first dielectric layer forming step. Inthese layer forming steps, these layers can be formed by, for example, asputtering method or a vapor deposition method.

In the etching step, the grid-shaped convex portion which is arranged onthe transparent substrate at the pitch shorter than the wavelength oflight of a use band is formed by selectively etching the laminationstructure formed by the above-described layer forming steps.Specifically, a one-dimensional lattice-shaped mask pattern is formedby, for example, photolithography or nanoimprinting. Then, thegrid-shaped convex portion which is arranged on the transparentsubstrate at the pitch shorter than the wavelength of light of a useband is formed by selectively etching the lamination structure. As theetching method, for example, a dry etching method using an etching gascorresponding to an etching object can be exemplified.

Particularly, in the invention, the reflection layer and the firstdielectric layer are formed to have substantially the same width and theminimum width of the absorption layer is set to be smaller than theminimum width of the reflection layer and the first dielectric layer bychanging a balance with the combination of isotropic etching andanisotropic etching.

In addition, the polarizing plate manufacturing method of the inventionmay include a step of coating the surface with a protection film formedof a dielectric. Further, the polarizing plate manufacturing method ofthe invention may include a step of coating the surface with an organicwater-repellent film.

Optical Apparatus

An optical apparatus of the invention includes the above-describedpolarizing plate according to the invention. The polarizing plateaccording to the invention can be used for various applications. As theoptical apparatus to be applied, for example, a liquid crystalprojector, a head-up display, a digital camera, and the like can beexemplified. In particular, since the polarizing plate according to theinvention is an inorganic polarizing plate having excellent heatresistance, the polarizing plate can be appropriately used for a liquidcrystal projector, a head-up display, and the like requiring heatresistance as compared with an organic polarizing plate formed of anorganic material.

When the optical apparatus according to the invention includes aplurality of polarizing plates, at least one of the plurality ofpolarizing plates may be the polarizing plate according to theinvention. For example, when the optical apparatus according to theembodiment is a liquid-crystal projector, at least one of the polarizingplates disposed on the incident side and the emission side of the liquidcrystal panel may be the polarizing plate according to the invention.

According to the polarizing plate, the polarizing plate manufacturingmethod, and the optical apparatus of the invention, the followingeffects are obtained.

The polarizing plate according to the invention has the wire gridstructure including the transparent substrate and the grid-shaped convexportion arranged on the transparent substrate at the pitch shorter thanthe wavelength of light of a use band and extending in a predetermineddirection, in which the reflection layer, the first dielectric layer,and the absorption layer are provided on the grid-shaped convex portionin order from the transparent substrate and a relationship of theminimum width of the reflection layer, the first dielectric layer, andthe absorption layer as viewed from the predetermined direction isspecified, thereby exhibiting an effect of shifting the wavelength rangeof the light absorbing action. As a result, the reflectancecharacteristics are excellently controlled. Thus, according to theinvention, it is possible to provide the polarizing plate 10 capable ofexcellently controlling the reflectance characteristics, the polarizingplate manufacturing method, and the optical apparatus including thepolarizing plate.

EXAMPLES

Next, examples of the invention will be described, but the invention isnot limited to these examples.

Example 1 and Comparative Example 1 Preparation of Polarizing Plate

In Example 1, the polarizing plate 10 having a structure illustrated inFIG. 1 and optimized to each of the green band (wavelength λ=520 to 590nm), the blue band (wavelength λ=430 to 510 nm), and the red band(wavelength λ=600 to 680 nm) was prepared and was provided forsimulation. Further, as Comparative Example 1, a polarizing plate 20different from the polarizing plate 10 of Example 1 only in thestructure of the absorption layer 4 was prepared and was provided forsimulation. The polarizing plate 20 of Comparative Example 1 has astructure illustrated in FIG. 2, the absorption layer 4 has arectangular shape as viewed from the extension direction of thegrid-shaped convex portion 6 (a predetermined direction: the Y-axisdirection), that is, in a cross-sectional view orthogonal to thepredetermined direction, and the reflection layer 2 and the firstdielectric layer 3 are formed to have substantially the same width.

Simulation Method

The optical characteristics of the polarizing plate 10 and thepolarizing plate 20 were verified by electromagnetic field simulationaccording to a rigorous coupled wave analysis (RCWA) method. For thesimulation, grating simulator Gsolver manufactured from Grating SolverDevelopment was used.

Simulation Result

FIG. 3 is a graph showing a result obtained by verifying a relationshipbetween the wavelength and the absorption axis reflectance for thepolarizing plate 10 and the polarizing plate 20 optimized to the greenband (wavelength λ=520 to 590 nm). FIG. 4 is a graph showing a resultobtained by verifying a relationship between the wavelength and theabsorption axis reflectance for the polarizing plate 10 and thepolarizing plate 20 optimized to the blue band (wavelength λ=430 to 510nm). FIG. 5 is a graph showing a result obtained by verifying arelationship between the wavelength and the absorption axis reflectancefor the polarizing plate 10 and the polarizing plate 20 optimized to thered band (wavelength λ=600 to 680 nm).

In FIGS. 3 to 5, the horizontal axis indicates the wavelength λ (nm) andthe vertical axis indicates the absorption axis reflectance (%). Here,the absorption axis reflectance means the reflectance of the polarizedlight (TE wave) incident to the polarizing plate in the absorption axisdirection (the Y-axis direction). Further, in FIGS. 3 to 5, a graphindicated by a dashed line shows the result of the polarizing plate 10of the invention corresponding to Example 1 and a graph indicated by asolid line shows the result of the polarizing plate 20 corresponding toComparative Example 1.

As shown in FIGS. 3 to 5, when the polarizing plate 10 of Example 1 iscompared with the polarizing plate 20 of Comparative Example 1, thewaveform position is shifted so that the absorption axis reflectance issuppressed to be low in all of the green band (wavelength λ=520 to 590nm), the blue band (wavelength λ=430 to 510 nm), and the red band(wavelength λ=600 to 680 nm).

FIG. 6 is a graph showing a result obtained by verifying a relationshipbetween the volume of the absorption layer and the absorption axisreflectance in the green band (wavelength λ=520 to 590 nm) for thepolarizing plate 10 and the polarizing plate 20 optimized to the greenband (wavelength λ=520 to 590 nm) by simulation. FIG. 7 is a graphshowing a result obtained by verifying a relationship between the volumeof the absorption layer and the absorption axis reflectance in the blueband (wavelength λ=430 to 510 nm) for the polarizing plate 10 and thepolarizing plate 20 optimized to the blue band (wavelength λ=430 to 510nm) by simulation. FIG. 8 is a graph showing a result obtained byverifying a relationship between the volume of the absorption layer andthe absorption axis reflectance in the red band (wavelength λ=600 to 680nm) for the polarizing plate 10 and the polarizing plate 20 optimized tothe red band (wavelength λ=600 to 680 nm) by simulation.

In FIGS. 6 to 8, the horizontal axis indicates the volume of theabsorption layer and the vertical axis indicates the absorption axisreflectance (%). Here, as described above, the absorption axisreflectance means the reflectance of the polarized light (TE wave)incident to the polarizing plate in the absorption axis direction (theY-axis direction). In FIGS. 6 to 8, a point in which the volume of theabsorption layer becomes 100% shows the result of the polarizing plate20 corresponding to Comparative Example 1 and a range in which thevolume becomes smaller than 100% shows the result of the polarizingplate 10 of the invention corresponding to Example 1.

As shown in FIGS. 6 to 8, since the polarizing plate 10 of Example 1 cancontrol the reflectance characteristics in all of the green band(wavelength λ=520 to 590 nm), the blue band (wavelength λ=430 to 510nm), and the red band (wavelength λ=600 to 680 nm) by shifting thewaveform position with a change in volume of the absorption layer, thepolarizing plate can be optimized.

Example 2 and Comparative Example 2 Preparation of Polarizing Plate

In Example 2, the polarizing plate 30 having a structure illustrated inFIG. 9 and optimized to each of the green band (wavelength λ=520 to 590nm), the blue band (wavelength λ=430 to 510 nm), and the red band(wavelength λ=600 to 680 nm) was prepared and was provided forsimulation. Further, as Comparative Example 2, a polarizing plate 40different from the polarizing plate 30 of Example 2 only in thestructure of the absorption layer 4 was prepared and was provided forsimulation. The polarizing plate 40 of Comparative Example 2 has astructure illustrated in FIG. 10, the absorption layer 4 has arectangular shape as viewed from the extension direction of thegrid-shaped convex portion 6 (a predetermined direction: the Y-axisdirection), that is, in a cross-sectional view orthogonal to thepredetermined direction and the reflection layer 2 and the firstdielectric layer 3 are formed to have substantially the same width.

Simulation Method

The optical characteristics of the polarizing plate 30 and thepolarizing plate 40 were verified by electromagnetic field simulationaccording to a rigorous coupled wave analysis (RCWA) method. For thesimulation, grating simulator Gsolver manufactured from Grating SolverDevelopment was used.

Simulation Result

FIG. 11 is a graph showing a result obtained by verifying a relationshipbetween the wavelength and the absorption axis reflectance for thepolarizing plate 30 and the polarizing plate 40 optimized to the greenband (wavelength λ=520 to 590 nm). FIG. 12 is a graph showing a resultobtained by verifying a relationship between the wavelength and theabsorption axis reflectance for the polarizing plate 30 and thepolarizing plate 40 optimized to the blue band (wavelength λ=430 to 510nm). FIG. 13 is a graph showing a result obtained by verifying arelationship between the wavelength and the absorption axis reflectancefor the polarizing plate 30 and the polarizing plate 40 optimized to thered band (wavelength λ=600 to 680 nm).

In FIGS. 11 to 13, the horizontal axis indicates the wavelength λ (nm)and the vertical axis indicates the absorption axis reflectance (%).Here, the absorption axis reflectance means the reflectance of thepolarized light (TE wave) incident to the polarizing plate in theabsorption axis direction (the Y-axis direction). Further, in FIGS. 11to 13, a graph indicated by a dashed line shows the result of thepolarizing plate 30 of the invention corresponding to Example 2 and agraph indicated by a solid line shows the result of the polarizing plate40 corresponding to Comparative Example 2.

As shown in FIGS. 11 to 13, when the polarizing plate 30 of Example 2 iscompared with the polarizing plate 40 of Comparative Example 2, thewaveform position is shifted so that the absorption axis reflectance issuppressed to be low in all of the green band (wavelength λ=520 to 590nm), the blue band (wavelength λ=430 to 510 nm), and the red band(wavelength λ=600 to 680 nm).

FIG. 14 is a graph showing a result obtained by verifying a relationshipbetween the volume of the absorption layer and the absorption axisreflectance in the green band (wavelength λ=520 to 590 nm) for thepolarizing plate 30 and the polarizing plate 40 optimized to the greenband (wavelength λ=520 to 590 nm) by simulation. FIG. 15 is a graphshowing a result obtained by verifying a relationship between the volumeof the absorption layer and the absorption axis reflectance in the blueband (wavelength λ=430 to 510 nm) for the polarizing plate 30 and thepolarizing plate 40 optimized to the blue band (wavelength λ=430 to 510nm) by simulation. FIG. 16 is a graph showing a result obtained byverifying a relationship between the volume of the absorption layer andthe absorption axis reflectance in the red band (wavelength λ=600 to 680nm) for the polarizing plate 30 and the polarizing plate 40 optimized tothe red band (wavelength λ=600 to 680 nm) by simulation.

In FIGS. 14 to 16, the horizontal axis indicates the volume of theabsorption layer and the vertical axis indicates the absorption axisreflectance (%). Here, as described above, the absorption axisreflectance means the reflectance of the polarized light (TE wave)incident to the polarizing plate in the absorption axis direction (theY-axis direction). In FIGS. 14 to 16, a point in which the volume of theabsorption layer becomes 100% shows the result of the polarizing plate40 corresponding to Comparative Example 2 and a range in which thevolume becomes smaller than 100% shows the result of the polarizingplate 30 of the invention corresponding to Example 2.

As shown in FIGS. 14 to 16, since the polarizing plate 30 of Example 2can control the reflectance characteristics in all of the green band(wavelength λ=520 to 590 nm), the blue band (wavelength λ=430 to 510nm), and the red band (wavelength λ=600 to 680 nm) by shifting thewaveform position with a change in volume of the absorption layer, thepolarizing plate can be optimized.

EXPLANATION OF REFERENCE NUMERALS

10, 20, 30, 40, 50, 60 POLARIZING PLATE

1 TRANSPARENT SUBSTRATE

2 REFLECTION LAYER

3 FIRST DIELECTRIC LAYER

4 ABSORPTION LAYER

5 SECOND DIELECTRIC LAYER

6 GRID-SHAPED CONVEX PORTION

P PITCH OF GRID-SHAPED CONVEX PORTION

W WIDTH

L LIGHT

What is claimed is:
 1. A polarizing plate with a wire grid structure,comprising: a transparent substrate; and a grid-shaped convex portionwhich is arranged on the transparent substrate at a pitch shorter than awavelength of light of a use band and extends in a predetermineddirection, wherein the grid-shaped convex portion includes a reflectionlayer, a first dielectric layer, and an absorption layer in order fromthe transparent substrate, and wherein as viewed from the predetermineddirection, the reflection layer and the first dielectric layer havesubstantially the same width, a minimum width of the absorption layer issmaller than a minimum width of the reflection layer and the firstdielectric layer and the absorption layer is substantially isoscelestrapezoidal, and wherein the first dielectric layer is formed of Sioxide.
 2. The polarizing plate according to claim 1, wherein a seconddielectric layer is provided on a surface of the absorption layer thatis opposite to the first dielectric layer in the absorption layer, andwherein the minimum width of the absorption layer is smaller than aminimum width of the second dielectric layer as viewed from thepredetermined direction.
 3. The polarizing plate according to claim 1,wherein the reflection layer is substantially rectangular as viewed fromthe predetermined direction.
 4. The polarizing plate according to claim1, wherein the first dielectric layer is substantially rectangular asviewed from the predetermined direction.
 5. The polarizing plateaccording to claim 1, wherein the transparent substrate is transparentto a wavelength of light of a use band and is formed of glass, crystal,or sapphire.
 6. The polarizing plate according to claim 1, wherein thereflection layer is formed of aluminum or aluminum alloy.
 7. Thepolarizing plate according to claim 1, wherein the first dielectriclayer is formed of Si oxide.
 8. The polarizing plate according to claim2, wherein the second dielectric layer is formed of Si oxide.
 9. Thepolarizing plate according to claim 1, wherein the absorption layerincludes Fe or Ta and also includes Si.
 10. The polarizing plateaccording to claim 1, wherein a surface of the polarizing plate to whichlight is incident is covered with a protection film formed of adielectric.
 11. The polarizing plate according to claim 1, wherein asurface of the polarizing plate to which light is incident is coveredwith an organic water-repellent film.
 12. A method of manufacturing apolarizing plate with a wire grid structure, comprising: a reflectionlayer forming step of forming a reflection layer on a first surface of atransparent substrate; a first dielectric layer forming step of forminga first dielectric layer on a surface of the reflection layer that isopposite to the first surface of the transparent substrate; anabsorption layer forming step of forming an absorption layer on asurface of the first dielectric layer that is opposite to the surface ofthe reflection layer; and an etching step of forming a grid-shapedconvex portion to be arranged on the transparent substrate at a pitchshorter than a wavelength of light of a use band by selectively etchinga formed lamination structure, wherein in the etching step, thereflection layer and the first dielectric layer are formed to havesubstantially a same width and a minimum width of the absorption layeris set to be smaller than a minimum width of the reflection layer andthe first dielectric layer by combining isotropic etching andanisotropic etching.
 13. An optical apparatus comprising: the polarizingplate according to claim
 1. 14. The polarizing plate according to claim2, wherein the reflection layer is substantially rectangular as viewedfrom the predetermined direction.
 15. The polarizing plate according toclaim 14 wherein the reflection layer is formed of aluminum or aluminumalloy.
 16. The polarizing plate according to claim 2 wherein theabsorption layer includes Fe or Ta and also includes Si.
 17. Thepolarizing plate according to claim 2, wherein a surface of thepolarizing plate to which light is incident is covered with a protectionfilm formed of a dielectric.
 18. The polarizing plate according to claim2, wherein the first dielectric layer is substantially rectangular asviewed from the predetermined direction.
 19. The polarizing plateaccording to claim 18, wherein the first dielectric layer is formed ofSi oxide.
 20. The polarizing plate according to claim 2, wherein asurface of the polarizing plate to which light is incident is coveredwith an organic water-repellent film.